1. Field of the Invention
The present invention relates to an image forming device for forming images using developer. Further, the present invention relates to a developing unit of the image forming device. Moreover, the present invention also relates to an image forming device main body attached to the developing unit.
2. Description of the Related Art
Image forming devices that utilize developer to print onto a recording medium (printing paper, for example) are well known. For example, a laser printer comprises a laser printer main body, and a developing unit attached detachably thereto.
The laser printer main body has a main case including a space for housing the developing unit, and a photoreceptor disposed in a position facing the space. The photoreceptor supports an electrostatic latent image.
The developing unit has a case for housing toner, and a developing roller supported rotatably by the toner case. While the developing unit is attached to the laser printer main body, the photoreceptor and the developing roller both rotate while making contact with one another. The developing roller supplies toner housed in the toner case to the photoreceptor. The toner thus adheres to an area of the photoreceptor on which the electrostatic latent image is formed, and the electrostatic latent image of the photoreceptor becomes visible. The toner that has become visible is transferred from the photoreceptor to the recording medium, thus forming words or images on the recording medium.
In order to form a visible image having a uniform thickness on the photoreceptor, it is preferred that the developing roller presses the photoreceptor with a constant amount of force. For this purpose, a pushing member may be formed on the laser printer main body. This pushing member pushes the toner case in a direction where the developing roller presses the photoreceptor.
Further, a laser printer that performs color printing using four colors of toner is provided with four photoreceptors and four developing units. Each of the developing units houses a different color toner. When the photoreceptors and the developing rollers of the developing units have been brought into contact, the different color toners are supplied to the photoreceptors. Color printing can thus be performed. Alternatively, in the case where monochromatic printing is performed, toner may be supplied to only one photoreceptor. The developing roller may therefore be brought into contact with only the relevant photoreceptor, and the other developing rollers may be separate from the other three photoreceptors. In order to realize this operation, the laser printer main body may be provided with a pushing member. This pushing member pushes the toner case in a direction where the developing rollers separate from the photoreceptors.
U.S. Pat. No. 6,751,428 teaches a developing unit having a protruding member that protrudes from a toner case. The protruding member is fixed to the toner case. With this developing unit, a developing roller is pressed against a photoreceptor by the protruding member being pushed from a laser printer main body.